1. Field of the Invention
The present invention relates to a plane light source and an LCD backlight unit having the same, and more particularly, to a plane light source that increases efficiency and reduces the number of light emitting devices by optimizing the arrangement and pitch of a plurality of light emitting devices, and an LCD backlight unit having the same.
2. Description of the Related Art
In general, cold cathode fluorescent lamps (CCFLs) that are used as light sources of liquid crystal displays (LCDs) according to the related art use mercury gas. For this reason, the CCFL may cause environmental contamination, has low response speed and lower color reproducibility, and may not lead to a reduction in size, thickness, and weight of an LCD panel.
Contrary to the CCFL, a light emitting diode (LED) is environment-friendly, has a response speed of several nanoseconds so as to achieve high-speed response and be effective for a video signal stream, and allows impulsive driving. Further, the LED has a color reproducibility of 100% or more, varies in luminance, color temperature, and the like by controlling the intensity of light of red, green, and blue LEDs, and can result in a reduction in size, thickness, and weight of the LCD panel. Accordingly, the LED has been widely used as a light source for the backlight unit of the LCD panel or the like.
The LCD backlight using the LEDs may be divided into an edge type backlight and a direct type backlight according to the position of a light source. In a case of the edge type backlight, a bar-shaped CCFL having width larger than length is positioned at the side thereof and emits light onto a front surface of the LCD panel by using a light guide panel. In a case of the direct type backlight, a plane light source is positioned at a lower part of the LCD panel, and light is directly irradiated to a front surface of the LCD panel from the plane light source that has almost the same area as the LCD panel.
FIG. 1 is a view illustrating an arrangement of light emitting devices in a plane light source according to the related art.
As shown in FIG. 1, a plane light source 100 that is used in a direct type LCD panel according to the related art includes a plurality of LEDs 102 that are arranged in rows and columns at a substrate 101. Here, it may be considered that four neighboring LEDs 102 of the plurality of LEDs 102 form a rectangle.
However, such an arrangement requires a larger number of LEDs used to cover the same light emitting area than necessary.
Further, a difference in brightness between an area adjacent to each LED 102 and an area distant from the LED 102, specifically, the center of the rectangle formed by the four LEDs 102 may be large. That is, when a number of LEDs 102 are arranged, uniformity of brightness may be achieved. However, when the number of LEDs is reduced to improve efficiency as described above, the distance between the neighboring LEDs becomes larger. This may cause a change in brightness distribution.
Therefore, for a plane light source used in the LCD panel or the like, there is a need for a method of improving the performance of the plane light resource by reducing the number of light emitting devices used in the plane light source to cause little difference in brightness, that is, achieve uniformity of luminance.